Many species of plants, plant pathogens, insects, and animals are considered pests in that they reduce agricultural productivity, diminish aesthetics and economic value of ornamental plants and threaten the health of natural resources such as forest, rangeland and aquatic environments. For instance, invasive plants and plant pathogens, such as, for example, dwarf mistletoe, weedy Rubus spp., leafy spurge, clidemia and miconia shrubs, kudzu, Annosnum root rot, beech bark disease, and frosty pod rot, often grow unimpeded and can supplant or destroy native plant species. Similarly, insects like Asian longhorn beetles, emerald ash borers, gypsy moths, hemlock wooly adelgid, bark beetles, Douglas-fir tussock moth, western spruce budworm, pear thrips, and elongate hemlock scale, attack healthy trees, plants, and other flora in a manner that is detrimental to the well being of such trees, plants and other flora and as a consequence, detrimental to other plants and animals native to the forest environment. Diseases and other pests of, but not limited to, agricultural crops, ornamentals and turf are numerous. Pest species require management if desirable characteristics of their hosts are to be preserved.
Many approaches for managing these threats rely almost exclusively on synthetic chemical pesticides. Although such pesticides may be effective at controlling undesirable organisms, increased awareness about the adverse effects of these chemical compositions on water quality, non-targeted species, and humans provides motivation to introduce safer alternatives. Among alternatives being studied, biologically-based compositions that use fungi (“biopesticides”) are showing significant promise when used to control populations of certain targeted pests. These biopesticides are effective because they produce spores, conidia, mycelium, and other fungal units (hereinafter collectively, “spores”) that infect healthy targeted pests in a manner that causes disease and, eventually, death.
Despite the desirable pathogenic effects that these biopesticides display, inadequate and cost effective production and delivery approaches are limiting their widespread adoption. Spore production, for instance, is often accomplished in limited batches or in facilities that require substantial capital investment to produce quantities of spores suitable for a biopesticide application. Balanced against these high production costs are the health and safety benefits, reduced ecological impact, and value added potential, e.g., organic labeling, derived by pest management and forest preservation that use biopesticides instead of chemicals. Unfortunately, without significant reduction in the fixed costs associated with spore production, this balance often tips in favor of the known chemical pesticides.
The efficacy of a biopesticide is often limited by physical constraints associated with its formulation, such as, for example, relatively high viscosity of low volume applications containing sufficient spores (1×1013 spores/acre) that does not meet the requirements for effective aerial applications. Because many biopesticides cannot be effectively applied to a target region, e.g., a forest, they are unable to provide the required number and concentration of spores for effective pest management. Without providing the proper concentration of the spores after delivery, the biopesticidal composition will not be an effective substitute for the chemical pesticides described above.
Known pest management practices involving the use of biopesticide compositions typically have a high concentration of spores to achieve effective mortality of the targeted pests. Such concentrations are often in excess of 1×108 spores/ml (of the biopesticide composition) when 200 liter/acre are applied, and concentration increases as delivery volume is reduced. Such practices that use high numbers of spores are often not economically viable because of the relatively high cost of producing the number of spores required to meet the desired rates of pest mortality. Accordingly, farm managers, agriculturists, foresters and others seeking to implement biological control agents as part of their management regimes would welcome a biopesticide solution that can increase the concentration of the spores after delivery so as to improve the efficacy and economics of the biopesticide technique.